A. Field of the Invention
This invention is directed to an interactive workstation and associated computerized techniques for facilitating detection of individual teeth boundaries and gingival boundaries from a three-dimensional virtual computer model of teeth. The identification and separation of the teeth from the gingival tissue has applications in digital dentistry and orthodontics. For example, the separation of the teeth from the gingiva is typically a preliminary step in planning of treatment for orthodontic patients on a computer.
B. Description of Related Art
The traditional process of diagnosis and treatment planning for a patient with orthodontic problems or disease typically consists of the practitioner obtaining clinical history, medical history, dental history, and orthodontic history of the patient supplemented by 2D photographs, 2D radiographic images, CT scans, 2D and 3D scanned images, ultrasonic scanned images, and in general non-invasive and sometimes invasive images, plus video, audio, and a variety of communication records. Additionally, physical models, such as made from plaster of Paris, of the patient's teeth are created from the impressions taken of the patient's upper and lower jaws. Such models are manually converted into teeth drawings by projecting teeth on drawing paper. Thus, there is a large volume of images and data involved in the diagnosis and treatment planning process. Furthermore, the information may require conversion from one form to another and selective reduction before it could become useful. There are some computerized tools available to aid the practitioner in these data conversion and reduction steps, for example to convert cephalometric x-rays (i.e., 2 dimensional x-ray photographs showing a lateral view of the head and jaws, including teeth) into points of interest with respect to soft tissue, hard tissue, etc., but they are limited in their functionalities and scope. Even then, there is a fairly substantial amount of manual work involved in these steps.
Additionally, the physical molds of the patient's dentition are converted into physical models such that each tooth can be moved and repositioned individually. However, such models allow free movement of teeth without regard to the patient's biological constraints, and can frequently lead to impractical treatment set-ups.
Furthermore, a number of measurements, e.g., available space between teeth, are also often done manually. Generally, these steps are time consuming and prone to inherent inaccuracies. Furthermore, the practitioner has to contend with the biological interdependencies within the patient, which introduces constraints eliminating certain treatment options that would otherwise be acceptable, between the soft tissue, the hard tissue, and the teeth. There is lack of an integrated platform which a practitioner could utilize to filter-out non-practicable treatment options.
Consequently, the practitioner is left to mental visualization, chance process to select the treatment course that would supposedly work. Furthermore, the diagnosis process is some-what ad-hoc and the effectiveness of the treatment depends heavily upon the practitioner's level of experience. Often, due to the complexities of the detailed steps and the time consuming nature of them, some practitioners take a short cut, relying predominantly on their intuition to select a treatment plan. For example, the diagnosis and treatment planning is often done by the practitioner on a sheet of acetate over the X-rays. All of these factors frequently contribute towards trial and error, hit-and-miss, lengthy and inefficient treatment plans that require numerous mid-course adjustments. While at the beginning of treatment things generally run well as all teeth start to move at least into the right direction, at the end of treatment a lot of time is lost by adaptations and corrections required due to the fact that the end result has not been properly planned at any point of time. By and large, this approach lacks reliability, reproducibility and precision. More over, there is no comprehensive way available to a practitioner to stage and simulate the treatment process in advance of the actual implementation to avoid the often hidden pitfalls. And the patient has no choice and does not know that treatment time could be significantly reduced if proper planning was done.
In recent years, computer-based approaches have been proposed for separating teeth in patient's 3D dentition model. A 3D scanned model of a patient's dentition, whether taken in-vivo or from a physical model, typically covers the surfaces of all teeth and parts of the surrounding gum, but there can also be gaps in it, i.e. parts of teeth and gum the 3D scan did not reach. Given this data, the present invention is directed to a procedure to analyze the data and to determine which portions of the scanned data correspond to the gums and which portions correspond to the individual. Thus, both the transitions between the teeth and the gums and those between adjoining teeth are detected, and the portions between these transitions are correctly assigned to the corresponding portions of the scanned jaw.
Cheang et al., U.S. Pat. No. 6,371,761, describe a method using flexible plane for separating teeth wherein a computer-implemented method separates first and second portions of a tooth by defining a cutting surface intersecting the first and second portions; and applying the cutting surface to the to the tooth to separate the tooth into two portions. Pavlovskaia, et al, U.S. Pat. No. 6,386,878, and U.S. Patent Application Publication 2002/0177108 describe a method using cutting surface for removing gingival tissue from teeth wherein a computer-implemented method removes gingival from a model of a tooth by defining a cutting surface along the gingiva; and applying the cutting surface to the to the tooth to separate the gingival from the in a single cut. Jones et al., U.S. Pat. No. 6,409,504, and in related U.S. Patent Application Publication 2003/0039389, and U.S. Patent Application Publication 2002/0102009, describe a method for manipulating a digital dentition model to form models of individual dentition components wherein computer-automated techniques are described using “voxel representation” and “geometric representation” of a 3D model. Pavlovskaia, et al, U.S. Pat. No. 6,463,344, describe a computer-implemented method that generates a computer model of one or more teeth, by receiving as input a digital data set of meshes representing the teeth; creating a parametric representation of the digital data set; and displaying the computer model of the teeth using the parametric representation. Chisti et al, U.S. Published Patent Application 2003/0039941, describe digitally modeling the deformation of gingival tissue during orthodontic treatment.
In recent years, computer-based approaches have been proposed for aiding orthodontists in their practice. However, these approaches are limited to diagnosis and treatment planning of craniofacial structures, including the straightening of teeth. See Andreiko, U.S. Pat. No. 6,015,289; Snow, U.S. Pat. No. 6,068,482; Kopelmann et al., U.S. Pat. No. 6,099,314; Doyle, et al., U.S. Pat. No. 5,879,158; Wu et al., U.S. Pat. No. 5,338,198, and Chisti et al., U.S. Pat. Nos. 5,975,893 and 6,227,850, the contents of each of which is incorporated by reference herein.
A method for generation of a 3D model of the dentition from an in-vivo scan of the patient, and interactive computer-based treatment planning for orthodontic patients, is described in published PCT patent application of OraMetrix, Inc., the assignee of this invention, publication no. WO 01/80761, the contents of which are incorporated by reference herein. The PCT application, at pages 73 and 75, describes several methods for separating teeth from a virtual model, using user interaction and virtual tooth models. The application suggests that tooth separation could be done using an automated algorithm looking for grooves between tooth crowns and gingival tissue, but does not describe what that algorithm might be or describe how the process would work.
Other background references related to capturing three dimensional models of dentition and associated craniofacial structures include S. M. Yamany and A. A. Farag, “A System for Human Jaw Modeling Using Intra-Oral Images” in Proc. IEEE Eng. Med. Biol. Soc. (EMBS) Conf., Vol. 20, Hong Kong, October, 1998, pp. 563-566; and M. Yamany, A. A. Farag, David Tasman, A. G. Farman, “A 3-D Reconstruction System for the Human Jaw Using a Sequence of Optical Images,” IEEE Transactions on Medical Imaging, Vol. 19, No. 5, May 2000, pp. 538-547. The contents of these references are incorporated by reference herein.